The present disclosure relates to a fixing device and an image forming apparatus.
A general configuration of a fixing device that fixes a toner to a sheet is provided with a rotatable heating member (such as a fixing roller and a fixing belt), a pressing roller coming into contact with the heating member and a pressing mechanism that forms a pressing region in which the sheet is to be sandwiched and conveyed between the pressing roller and the heating member. By the heat and pressure in the pressing region, the toner is fixed to the sheet. In addition, the fixing device is often configured to be able to be pulled out from a main body of an image forming apparatus in view of workability at the time of removal of a jammed sheet or maintenance and servicing activity.
In the meantime, the fixing device enables release of the pressing by the pressing mechanism for the purpose of reduction of wrinkles in an envelope or a thin sheet. In addition, in recent years, from a request for energy saving, there is also a fixing device that is capable of setting an intermediate pressure state in which a predetermined pressing force is applied in advance in order to reduce a heating time, and thus a function of adjusting the pressing force is necessary. Accordingly, there may be a case in which a pressing mechanism is configured to convert a rotational force transmitted from a motor or the like, to the pressing force. In this case, in order to release the pressing, there is a need to remove the pressing force by a rotational force in an opposite direction to that at the time of the pressing. However, if the fixing device is pulled out from the main body of the image forming apparatus before the pressing is released, the sheet is hardly removed. The fixing device is also pulled out before the release of pressing is detected, and thus the image forming apparatus determines this pullout as an error and then issues a service call.
In addition, in recent years, a deceleration ratio of the rotational force is prone to be set at a higher value in view of the fact that a high load is applied, and it takes long time to release the pressing. Therefore, there is a high possibility that the fixing device is pulled out from the main body of the image forming apparatus before the pressing is released.
Conventionally, there is known a technique of bringing the fixing device into a pressing state or a pressing release state in synchronism with attachment or detachment of the fixing device to or from the main body of the image forming apparatus. For example, there is a technique in which a locking member and a cam are integrated with a lever, and when the lever is pushed down, the locking member engages with a notch of the main body of the image forming apparatus, and at the same time, the cam brings a pressing roller into the pressing state.
However, this technique is configured to manually actuate the locking member and the cam, and thus cannot be applied to the pressing mechanism that converts the rotational force transmitted from the motor to the pressing force.